Overcoming social determinants: World trade center health program monitoring use among the general responders

Abstract

Objective

In the United States, social determinants of health (SDOH) influence preventive health care, morbidity and mortality. As World Trade Center (WTC) general responders' morbidity has been associated with SDOH, we assessed whether their morbidity was associated with WTC Health Program participation.

Methods

Five clinical center staff (in New York/New Jersey) collect periodic program data. Adjusted linear, linear mixed model and generalized estimating equation regressions compared general responders' monitoring visits frequencies between January 1, 2008 (when annual monitoring was recommended) and December 31, 2024 in 15,515 members with marginalized and advantaged SDOH (age, sex, race, ethnicity, health care insurance, marital, educational, income occupational and primary language status) characteristics (excludes 7910 non-consenting; 6953 attending <2 visits; 6968 not seen after 2021; and 15,579 with missing data).

Results

No substantial (≥3 months) differences were observed. For example, Black (−0.8, 95% CI -1.3, −0.02) and Hispanic (−0.7, 95% CI -1.4, 0.1) members respectively attended monitoring visits approximately 0.75 months sooner than White and non-Hispanic members.

Conclusions

While the cohort has proportionately fewer people of color, women and elderly and more private health insurance coverage than the general population, the program has achieved remarkably similar health monitoring participation across the socio-economic spectrum.

Highlights

• •Health care utilization is influenced by social determinants of health.
• •The World Trade Center Health Program monitors General Responders health over time.
• •We compared societally marginalized-to-advantaged responders health monitoring.
• •The Program has surmounted societal inequities in health monitoring participation.

1. Introduction

Over the past 60 years, major efforts such as the Civil Rights Act and the Affordable Care Act, have aimed to reduce differences in health care use between marginalized and advantaged groups in the United States.(Hahn et al., 2018; Obama, 2016; SCOTUS., 2022) Yet, substantial differences persist across the social determinants of health (SDOH) such as income, health insurance coverage, ethnicity, race, education and occupation, including an income-based life expectancy gap of 10–15 years.(Bor et al., 2017; Dickman et al., 2017; NCHS., 2016) Lack of health care insurance is a major driver of reduced and delayed health care utilization, undermining early detection and case management.(Bailey et al., 2017; Biener and Zuvekas, 2019; Chetty et al., 2016; Dickman et al., 2017; Keisler-Starkey and Bunch, 2021; McWilliams, 2009; Shrider et al., 2021; Woolhandler and Himmelstein, 2017) In the U.S., Hispanic and Black individuals, as well as those who are unemployed or lack a high school diploma, experience the highest poverty rates and lowest levels of any type of health insurance coverage.(Keisler-Starkey and Bunch, 2021; Shrider et al., 2021) In the United States, privately insured individuals are diagnosed at earlier stages of cancer than those with Medicaid or no health care insurance.(Zhao et al., 2022).

Having health insurance is consistently associated with the earlier detection and treatment of hypertension, diabetes and high cholesterol and the two worldwide leading causes of adult mortality (cancer and cardiovascular disease) and with lower cause-specific and all-cause mortality rates.(Ahmad and Anderson, 2021; Hajek et al., 2021; McWilliams, 2009; Ott et al., 2009; Pinheiro et al., 2022; Wang et al., 2016; Woolhandler and Himmelstein, 2017; Zhao et al., 2022).

To serve the firefighters, general responders and others exposed to the toxic elements emanating from the September 11, 2001 attack on the World Trade Center (WTC), the Centers for Disease Control and Prevention (CDC) / National Institute for Occupational Safety and Health (NIOSH) established (July 2002), and over time, expanded the WTC Health Program (hereafter, “the program”).(Dasaro et al., 2017). Program eligibility is determined by the dates, duration, activities and location of responders' involvement, described elsewhere.(Dasaro et al., 2017) The program provides periodic physical and mental health monitoring at no cost to program members. On July 1, 2011, the program also began certifying various health conditions (known as WTC program-certified health conditions, https://www.cdc.gov/wtc/conditions.html) related to WTC exposures and providing qualifying treatment at no cost to program members.(Dasaro et al., 2017) General responders, the largest program member cohort, receive health monitoring at five Clinical Centers of Excellence located in New York and New Jersey.

Some research suggests that the program responders have better cancer survival than similar non-responders and/or the general population because they receive regular program health monitoring and earlier diagnosis.(Boffetta et al., 2022; Goldfarb et al., 2021; Khalifeh et al., 2023; Shapiro et al., 2020; Webber et al., 2021) Yet, SDOH characteristics associated with general population morbidity have similarly been associated with the WTC responders' morbidity.(Dasaro et al., 2025; Karasick et al., 2021; Shapiro et al., 2020; Sloan et al., 2021; Webber et al., 2021).

We hypothesized that the societal SDOH differences in preventive care use that influence early treatment, morbidity and mortality are not reflected in the socio-demographically diverse WTC General Responder Clinical Centers Cohort (GRCCC) health program monitoring participation. To test this hypothesis, we compared the monitoring program participation of members with marginalized SDOH characteristics to members with advantaged SDOH characteristics.

2. Methods

2.1. Study design and population

This is a prospective cohort study of the GRCCC members. Clinical staff collect periodic monitoring data using interview procedures that are standardized across the five centers. The first monitoring visit includes an interview about the members' socio-demographic characteristics and WTC-related exposures. At every monitoring visit, members are asked whether a physician has ever diagnosed or informed them they had any interview-specified or other physical health condition, and a mental health interview and comprehensive physical examination are conducted.

2.2. Measures

As the WTC Health Program expanded, various visit frequencies were recommended until 2008 when an annual visit recommendation was adopted and retained. To limit differences in understanding and adherence to variable visit-frequency guidance that could be associated with SDOH, all analyses were limited to data on or after January 1, 2008. The analyses include data captured through December 31, 2024 and exclude inactive members (not seen for any reason, including death, after December 31, 2021; Fig. 1). Some SDOH characteristics had large numbers of missing data (Fig. 1). As SDOH may be associated with data missingness, analyses exclude all members with any missing data. As such exclusions may limit the study's generalizability; analyses including separate “not reported” stratum in otherwise study-eligible members were performed for comparison. Of the 51,609 general responder program participants between 2008 and 2024, the primary analyses include 15,515 GRCCC who provided written informed consent for data aggregation and exclude 7910 non-consenting; 6953 attending <fewer than two visits; 6968 members not seen after 2021 and considered inactive; and 15,579 with missing SDOH or covariate data (Fig. 1).

Fig. 1.

Primary Analysis Flow Chart World Trade Center Health Program General Responder Clinical Centers Cohort monitoring visits, January 1, 2008 – December 31, 2024 World Trade Center Health Program General Responder Clinical Center of Excellence: Department of Environmental Medicine and Climate Science, Icahn School of Medicine at Mount Sinai, New York, NY; Department of Occupational Medicine, Epidemiology and Prevention, Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY; Department of Medicine, Stony Brook University Medical Center, Stony Brook, NY; NYU Langone Medical Center, New York University School of Medicine, New York, NY; Environmental and Occupational Health Sciences Institute, Rutgers University Biomedical Sciences, Piscataway, NJ. † counts are not mutually exclusive.

Two outcomes represent how often the program members attended the monitoring visits: (i) the average months between monitoring visits and (ii) the percentage of members' monitoring visit attendance ≤18 months apart. Both of these frequency outcomes were calculated using the average of all date differences between adjacent monitoring visits (e.g., visitdate_{2 –} visitdate₁ through visitdate_{last –} visitdate_last-1). Observations are included through each member's last visit, yielding a maximum follow-up of 17 years.

We also assessed the percent of the maximum number of monitoring visits attended (referred to as the “%MaxVisits”) to represent the general use of all possible monitoring visits. The %MaxVisits varies for each member depending upon their first visit date (visitdate₁), their total number of attended monitoring visits (Membervisits_n), and the largest number of visits made by any cohort member with the same visitdate₁ (Maxvisit_n). The %MaxVisits was calculated for each visitdate₁ as:

$$\%\text{MaxVisits}={100}^{\ast }{\text{Membervisits}}_{\mathrm{n}}/{\text{Maxvisit}}_{\mathrm{n}}$$

To avert the influence of outliers, we first (a priori) identified and used the 95th percentile of the data's Maxvisit_n, e.g., Maxvisit_n95%, as this outcome's denominator. For example, if visitdate₁ = January 1, 2014, Membervisits_n = 5, Maxvisit_n95% for January 1, 2014 = 10, the %MaxVisits = 50.0%; if instead Maxvisit_n95% for January 1, 2014 = 7, the %MaxVisits = 71.4%.

The analyses simultaneously adjusted for the following SDOH as categorical variables (‘advantaged’ reference groups specified in parentheses): race (White); ethnicity (Non-Hispanic); sex (male); type of health care insurance (private); and status at first visit marital (married), educational (college degree or higher), primary language (English), September 10, 2001 occupational (protective services) and 2001 income (≥$80,000 U.S. dollars/year) (Table 1). All others were considered marginalized groups. The frequency analyses adjusted for the member's age difference in five-year strata between adjacent monitoring visits whereas the %MaxVisits analyses adjusted for each member's average age across all visits. All analyses also adjust for three factors which may affect monitoring visit frequency: having a WTC program-certified health condition; the number of treatment visits for program-certified conditions; and, the monitoring visit clinic, to account for possible differences in access to care. Private health insurance included Medicare, line-of-duty insurance, and worker's compensation or other private insurance. Protective services occupations may not necessarily be advantageous compared with construction or telecommunications employment but was used as the occupationally advantaged reference group because it confers health care benefits and is the most reported GRCCC occupation.

Table 1.

World Trade Center General Responder Clinical Centers Cohort members first visit characteristics by the member's usual health insurance coverage across all visits, January 1, 2008 — December 31, 2024 (n = 31,094).

	Private†		Medicaid, Other Public		Not reported		Total
	(n = 28,750)		(n = 118)		(n = 2226)		(n = 31,094)
Characteristic	n	%	n	%	n	%	n	% of total n
Race
White	17,572	61.1	36	30.5	683	30.7	18,291	58.8
Black	2378	8.3	23	19.5	129	5.8	2530	8.1
Asian	348	1.2	0	0.0	13	0.6	361	1.2
Other	3054	10.6	43	36.4	475	21.3	3572	11.5
Not reported	5398	18.8	16	13.6	926	41.6	6340	20.4
Ethnicity:
Not Hispanic	18,835	65.5	≥46	≥39.0	801	36.0	19,689	63.3
Hispanic	4104	14.3	58	49.2	642	28.8	4804	15.5
Not reported	5811	20.2	NR	NR	783	35.2	6601	21.2
Age at visit1 (mean ± sd)	28,750	50.2 ± 9.3	118	48.8 ± 9.8	2226	50.8 ± 10.5	31,094	50.2 ± 9.3
Age on September 11, 2001 (mean ± sd)	28,750	37.8 ± 8.2	118	40.5 ± 9.9	2226	37.7 ± 8.6	31,094	37.8 ± 8.3
Sex
Male	22,466	87.0	163	69.4	2730	85.1	25,359	86.6
Female	3371	13.0	72	30.6	478	14.9	3921	13.4
Marital status
Married	20,768	72.2	59	50.0	1113	50.0	21,940	70.6
Single	3112	10.8	18	15.3	326	14.7	3456	11.1
Other	3596	12.5	≥33	≥28.0	364	16.4	3997	12.9
Not reported	1274	4.4	NR	NR	423	19.0	1701	5.5
Certified WTC covered condition
Certified (≥July 1, 2011)	22,123	77.0	105	89.0	1847	83.0	24,075	77.4
Not certified	6627	23.1	13	11.0	379	17.0	7019	22.6
Education
≥ College degree	8181	28.5	15	12.7	390	17.5	8586	27.6
High school diploma/some college	15,447	53.7	56	47.5	844	37.9	16,347	52.6
≤High school	1290	4.5	35	29.7	286	12.9	1611	5.2
Not reported	3832	13.3	12	10.2	706	31.7	4550	14.6
Primary Language
English	27,294	94.9	69	58.5	1685	75.7	29,048	93.4
Spanish	747	2.6	47	39.8	448	20.1	1242	4.0
Polish	208	0.7	0	0.0	56	2.5	264	0.9
Other	45	0.2	NR	NR	11	0.5	57	0.2
Not reported	456	1.6	NR	NR	26	1.2	483	1.6
Occupation on September 11, 2001
Protective services/military	16,738	58.2	NR	NR	680	30.6	17,427	56.1
Construction	3762	13.1	40	33.9	621	27.9	4423	14.2
Electric/Transportation	3538	12.3	13	11.0	285	12.8	3836	12.3
Unemployed	130	0.5	11	9.3	55	2.5	196	0.6
Other jobs	3864	13.4	41	34.8	492	22.1	4397	14.1
Not reported	718	2.5	NR	NR	93	4.2	815	2.6
Clinic
Mount Sinai	14,105	49.1	97	82.2	1267	56.9	15,469	49.8
NYU	1246	4.3	NR	NR	94	4.2	1348	4.3
Northwell Health	2192	7.6	NR	NR	305	13.7	2506	8.1
Rutgers	1160	4.0	0	0.0	324	14.6	1484	4.8
SUNY	10,047	35.0	NR	NR	236	10.6	10,287	33.1
2001 income
≥80 k USD	8158	28.4	NR	NR	293	13.2	8458	27.2
30-60 k USD	11,750	40.9	36	30.5	633	28.4	12,419	39.9
<30 k USD	1029	3.6	30	25.4	355	16.0	1414	4.6
Not reported	7813	27.2	≥38	≥32.20	945	42.5	8803	28.3
Entry into program:
≤2004	5772	20.1	48	40.7	528	23.7	6348	20.4
2005–2009	6968	24.2	46	39.0	530	23.8	7544	24.3
≥2010	16,010	55.7	24	20.3	1168	52.5	17,202	55.3

World Trade Center Health Program General Responder Clinical Center of Excellence: Department of Environmental Medicine and Climate Science, Icahn School of Medicine at Mount Sinai, New York, NY; Department of Occupational Medicine, Epidemiology and Prevention, Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY; Department of Medicine, Stony Brook University Medical Center, Stony Brook, NY; NYU Langone Medical Center, New York University School of Medicine, New York, NY; Environmental and Occupational Health Sciences Institute, Rutgers University Biomedical Sciences, Piscataway, NJ.

NYU = New York University; NR = Not reported; SUNY = State University of New York; USD = U.S. dollars.

† Includes private, Medicare, Workers Compensation, Line-Of-Duty Insurance.

†† Not reported as n < 10.

2.3. Statistical analysis

Descriptive analyses were stratified by the members' usual health insurance coverage to characterize the sample distributions and assessed using z-tests for differences in proportions and t-test for differences in means and standard deviations. The months between visits were assessed by linear mixed model regressions using within-patient random effects adjusted for all other variables were conducted, each using a random intercept and an autoregressive covariance structure that treats adjacent visits as more correlated than distant visits; proportionate weighting was used for the least squares estimators reference values (Table 2). Generalized estimating equations regression analyses using an exchangeable covariance structure assessed the odds of attending monitoring visits ≤18 months apart (Table 3). Linear regression analyses were conducted to assess the %MaxVisits (Table 4).

Table 2.

Average interval in months between adjacent monitoring visits among the General Responder Clinical Centers Cohort World Trade Center Health Program, January 1, 2008 — December 31, 2024^†.

	Members' visits		In members reporting care for hypertension, diabetes or high cholesterol††
	(n = 15,516; n visits = 121,072)		(n = 11,925; n visits = 54,696)
Characteristics	reference value	∆ (95% CI)	reference value	∆ (95% CI)
Age (5-year difference at visit)		-2.5 (−2.5, −2.4)		−1.7 (−1.7, −1.6)
Race
White	18.9 (18.7, 19.1)		16.9 (16.7, 17.1)
Black		−0.8 (−1.3, −0.2)		−0.5 (−1.0, 0.0)
Asian		−0.9 (−2.2, 0.4)		−0.8 (−2.0, 0.5)
Other		−1.6 (−2.4, −0.9)		−1.3 (−2.1, −0.5)
Ethnicity
Non-Hispanic	18.7 (18.7, 19.4).		16.7 (16.5, 16.9)
Hispanic		−0.7 (−1.4, 0.1)		−0.4 (−1.1, 0.3)
Health care insurance
Private	18.6 (18.4, 18.7)		16.7 (16.5, 16.8)
Public		−0.2 (−1.7, 1.2)		1.7 (−0.1, 3.4)
Sex
Male	18.5 (18.3 18.6)		16.6 (16.5, 16.8)
Female		0.8 (0.3, 1.3)		0.2 (−0.3, 0.7)
Marital status at first visit
Married	18.6 (18.4, 18.7)		16.5 (16.4, 16.6)
Single		0.0 (−0.4, 0.3)		−0.3 (−0.8, 0.1)
Other		0.1 (−0.1, 0.4)		0.2 (−0.2, 0.5)
Educational attainment at first visit
≥ College degree	17.9 (17.7, 18.2)		16.2 (15.9, 16.5)
High school diploma/some college		0.9 (0.6, 1.2)		0.7 (0.3, 1.0)
≤High school		1.7 (1.0, 2.5)		0.8 (0.0, 1.5)
Occupation on September 10, 2001
Protective services	19.7 (17.6, 21.8)		17.7 (15.7, 19.8)
Construction		2.0 (1.5, 2.5)		1.5 (1.0, 1.9)
Electrical/Transportation		1.6 (1.1, 2.2)		1.4 (0.9, 1.9)
Unemployed		1.8 (−0.2, 3.9)		1.7 (−0.4, 3.8)
Other		1.7 (1.3, 2.2)		1.4 (1.0, 1.9)
Primary language at first visit
English	18.6 (18.4, 18.7)		16.6 (16.5, 16.8)
Spanish		−0.6 (−1.7, 0.5)		0.1 (−0.9, 1.2)
Polish		1.7 (0.3, 3.2)		1.4 (0.1, 2.7)
Other		1.7 (−1.8, 5.3)		2.0 (−1.2, 5.2)
2001 annual income
≥80 k USD	19.4 (19.1, 19.7)		17.1 (16.9, 17.4)
30-80 k USD		−1.2 (−1.5, −0.9)		−0.7 (−1.0, −0.4)
≤30 k USD		−2.4 (−3.2, −1.6)		−1.2 (−2.0, −0.4)

World Trade Center Health Program General Responder Clinical Center of Excellence: Department of Environmental Medicine and Climate Science, Icahn School of Medicine at Mount Sinai, New York, NY; Department of Occupational Medicine, Epidemiology and Prevention, Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY; Department of Medicine, Stony Brook University Medical Center, Stony Brook, NY; NYU Langone Medical Center, New York University School of Medicine, New York, NY; Environmental and Occupational Health Sciences Institute, Rutgers University Biomedical Sciences, Piscataway, NJ.

† Mixed effects linear regressions using within-patient random effects analyses adjusted for all other table variables, visit clinic, number of treatment visits, and whether the participant had a program certified condition.

†† Excludes visits in which there was no report of current care for these conditions.

Table 3.

Odds ratios of making monitoring visits ≤18 months between General Responder Clinical Centers Cohort World Trade Center Health Program January 1, 2008 — December 31, 2024^†.

	Odds of visits ≤ 18 months	In members reporting care for hypertension, diabetes or high cholesterol, visits††	In members' including those not seen after December 31, 2021
	(n = 15,516; n visits = 121,072)	(n = 11,925; n visits = 54,696)	(n = 18,174; n visits = 130,344)
Characteristics	OR (95% CI)	OR	OR
Age at visit (5-year difference)	1.43 (1.41, 1.45)	1.31 (1.29, 1.33)	1.41 (1.39, 1.43)
Race
White	1.00 Reference	1.00 Reference	1.00 Reference
Black	1.11 (1.04, 1.20)	1.15 (1.06, 1.24)	1.12 (1.05, 1.20)
Asian	1.16 (0.96, 1.39)	1.26 (1.05, 1.53)	1.14 (0.97, 1.35)
Other	1.24 (1.11, 1.38)	1.32 (1.16, 1.51)	1.23 (1.11, 1.36)
Ethnicity
Non-Hispanic	1.00 Reference	1.00 Reference	1.00 Reference
Hispanic	1.05 (0.95, 1.17)	0.96 (0.85, 1.09)	1.08 (0.98, 1.19)
Health care insurance
Private	1.00 Reference	1.00 Reference	1.00 Reference
Public	0.76 (0.54, 1.07)	0.66 (0.41, 1.05)	0.81 (0.61, 1.07)
Sex
Male	1.00 Reference	1.00 Reference	1.00 Reference
Female	0.86 (0.80, 0.92)	0.94 (0.86, 1.02)	0.86 (0.81, 0.91)
Marital status at first visit
Married	1.00 Reference	1.00 Reference	1.00 Reference
Single	1.06 (0.99, 1.14)	1.13 (1.03, 1.24)	1.05 (0.99, 1.12)
Other	0.94 (0.89, 1.00)	0.92 (0.85, 0.98)	0.93 (0.89, 0.98)
Educational attainment at first visit
≥ College degree	1.00 Reference	1.00 Reference	1.00 Reference
High school diploma/some college	0.88 (0.84, 0.92)	0.89 (0.85, 0.95)	0.87 (0.84, 0.91)
≤High school	0.85 (0.76, 0.95)	0.84 (0.75, 0.95)	0.87 (0.79, 0.96)
Occupation on September 10, 2001
Protective services	1.00 Reference	1.00 Reference	1.00 Reference
Construction	0.76 (0.71, 0.81)	0.76 (0.70, 0.82)	0.76 (0.71, 0.81)
Electrical/Transportation	0.87 (0.80, 0.94)	0.85 (0.79, 0.93)	0.85 (0.80, 0.92)
Unemployed	0.74 (0.54, 1.01)	0.68 (0.50, 0.94)	0.71 (0.54, 0.93)
Other	0.81 (0.75, 0.87)	0.82 (0.76, 0.89)	0.78 (0.73, 0.83)
Primary language at first visit
English	1.00 Reference	1.00 Reference	1.00 Reference
Spanish	0.89 (0.77, 1.03)	0.95 (0.80, 1.12)	0.90 (0.79, 1.02)
Polish	0.72 (0.60, 0.87)	0.77 (0.63, 0.93)	0.74 (0.63, 0.86)
Other	0.53 (0.38, 0.75)	0.52 (0.34, 0.78)	0.55 (0.40, 0.75)
2001 annual income
≥80 k USD	1.00 Reference	1.00 Reference	1.00 Reference
30-80 k USD	1.19 (1.13, 1.24)	1.08 (1.03, 1.14)	1.17 (1.12, 1.22)
≤30 k USD	1.42 (1.26, 1.59)	1.12 (0.98, 1.27)	1.33 (1.20, 1.47)

World Trade Center Health Program General Responder Clinical Center of Excellence: Department of Environmental Medicine and Climate Science, Icahn School of Medicine at Mount Sinai, New York, NY; Department of Occupational Medicine, Epidemiology and Prevention, Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY; Department of Medicine, Stony Brook University Medical Center, Stony Brook, NY; NYU Langone Medical Center, New York University School of Medicine, New York, NY; Environmental and Occupational Health Sciences Institute, Rutgers University Biomedical Sciences, Piscataway, NJ.

† Mixed effects logistic regressions using within patient random effects analyses adjusted for all other table variables, visit clinic, number of treatment visits, and whether the member had a program certified condition.

†† Excludes visits in which there was no report of current care for these conditions.

Table 4.

Percent of the maximum number of visits made in General Responder Clinical Centers Cohort World Trade Center Health Program members January 1, 2008 — December 31, 2024^†,††.

	% Maximum Number of Visits	In members reporting care for hypertension, diabetes or high cholesterol‡	In members January 1, 2008 — February 29, 2020 (excludes COVID-19 period)
	(n = 15,516)	(n = 11,925)	(n members = 14,774)
Characteristics	% (95% CI)	% (95% CI)	% (95% CI)
Mean age across all visits	73.8 (73.5, 74.1)	75.6 (75.3, 76.0)	69.6 (69.2, 70.0)
Race
White	72.9 (72.5, 73.4)	75.0 (74.6, 75.5)	68.5 (68.0, 69.0)
Black	75.3 (74.2, 76.3)	77.6 (76.5, 78.7)	70.6 (69.4, 71.9)
Asian	75.4 (72.7, 78.1)	78.0 (75.2, 80.9)	71.1 (68.0, 74.3)
Other	76.6 (75.2, 78.0)	78.9 (77.4, 80.5)	73.5 (71.9, 75.2)
Ethnicity
Non-Hispanic	73.7 (73.3, 74.1)	76.0 (75.6, 76.5)	69.7 (69.2, 70.2)
Hispanic	74.0 (72.7, 75.3)	75.8 (74.4, 77.3)	69.0 (67.4, 70.5)
Health care insurance
Private	73.8 (73.5, 74.1)	76.0 (75.6, 76.3)	69.6 (69.2, 70.0)
Public	73.5 (68.8, 78.2)	76.2 (71.3, 81.1)	69.3 (63.9, 74.7)
Sex
Male	74.1 (73.7, 74.4)	76.1 (75.8, 76.5)	70.0 (69.6, 70.4)
Female	71.9 (70.9, 72.8)	74.9 (73.8, 76.0)	66.9 (65.7, 68.0)
Marital status at first visit
Married	73.7 (73.3, 74.1)	75.9 (75.5, 76.3)	69.4 (69.0, 69.9)
Single	75.0 (74.0, 76.0)	77.4 (76.3, 78.4)	71.4 (70.2, 72.5)
Other	73.1 (72.2, 74.0)	75.3 (74.4, 76.3)	68.7 (67.7, 69.8)
Educational attainment at first visit
≥ College degree	75.0 (74.5, 75.6)	77.1 (76.4, 77.7)	71.2 (70.5, 71.8)
High school diploma/some college	73.2 (72.7, 73.6)	75.5 (75.0, 75.9)	68.7 (68.2, 69.2)
≤High school	72.9 (71.4, 74.3)	75.2 (73.7, 76.8)	69.1 (67.4, 70.9)
Occupation on September 10, 2001
Protective services	74.3 (73.9, 74.8)	76.5 (76.0, 77.0)	70.1 (69.6, 70.6)
Construction	71.3 (70.4, 72.3)	73.8 (72.9, 74.8)	67.4 (66.3, 68.5)
Electrical/Transportation	73.9 (72.9, 74.9)	76.0 (75.0, 77.1)	69.7 (68.5, 70.9)
Unemployed	72.8 (68.5, 77.2)	76.4 (71.6, 81.1)	68.5 (63.4, 73.5)
Other	73.9 (73.0, 74.8)	76.1 (75.2, 77.1)	69.5 (68.5, 70.6)
Primary language at first visit
English	73.8 (73.4, 74.1)	76.0 (75.6, 76.4)	69.5 (69.1, 69.9)
Spanish	73.9 (71.7, 76.2)	75.6 (73.2, 77.9)	71.1 (68.5, 73.7)
Polish	75.4 (72.3, 78.5)	77.0 (73.9, 80.0)	73.6 (70.0, 77.2)
Other	69.1 (61.6, 76.6)	68.9 (61.4, 76.5)	66.6 (57.9, 75.2)
2001 annual income
≥80 k USD	73.2 (72.7, 73.8)	75.8 (75.2, 76.3)	68.9 (68.2, 69.5)
30-80 k USD	74.0 (73.5, 74.4)	76.1 (75.6, 76.5)	69.8 (69.3, 70.4)
≤30 k USD	75.1 (73.6, 76.7)	76.5 (74.8, 78.2)	71.3 (69.5, 73.1

World Trade Center Health Program General Responder Clinical Center of Excellence: Department of Environmental Medicine and Climate Science, Icahn School of Medicine at Mount Sinai, New York, NY; Department of Occupational Medicine, Epidemiology and Prevention, Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY; Department of Medicine, Stony Brook University Medical Center, Stony Brook, NY; NYU Langone Medical Center, New York University School of Medicine, New York, NY; Environmental and Occupational Health Sciences Institute, Rutgers University Biomedical Sciences, Piscataway, NJ.

† Linear regression analyses adjusted for all other table variables, visit clinic, number of treatment visits, and whether the participant had a program certified condition.

†† Percent maximum visits is the maximum number of possible visits based on their initial visit date; its denominator is the 95th percentile of maximum number of visits based on the initial visit date.

‡ Excludes visits in which there was no report of current care for these conditions.

To determine whether the program is being used differentially by members with comorbidities who may be more prone to use health care, comorbidity sensitivity analyses were limited to members who reported hypertension, diabetes and/or high cholesterol.(Hajek et al., 2021) Over half of the program members reported these conditions. Visits without a report of current care for these conditions were excluded from the comorbidity sensitivity analyses. To determine whether excluding inactive members influenced the frequency results, a sensitivity analysis assessed the odds of attending monitoring visits ≤18 months apart that included GRCCC members not seen after December 31, 2021. To determine whether the results were influenced by the COVID-19 pandemic, a sensitivity analysis of the %MaxVisits excluded visits made on or after March 1, 2020. To assess whether potential SDOH variable collinearity influenced the results, a minimally adjusted (age, race, sex, certification status and clinic affiliation) sensitivity analysis of the odds of attending monitoring visits ≤18 months apart was conducted.

All analyses were conducted using SAS version 9.4 (SAS Institute Inc.).

This research was approved by the Icahn School of Medicine at Mount Sinai Institutional Review Board (approval number 15–1266) and was conducted according to the World Medical Association Declaration of Helsinki (1975, revised 2013) and in accordance with national and institutional committees' standards regarding the protection of human subjects.

3. Results

As of December 31, 2024, the GRCCC, an open (i.e., continuing to enroll new participants) cohort, included 43,699 consenting program members with monitoring visits on or after 2008 (Fig. 1). Of these, the primary analyses included 15,515 active members (seen after 2021) with ≥2 monitoring visits and no missing data (Fig. 1).

3.1. Sample characteristics

As reported at their first visit, most GRCCC had private health insurance coverage, were White, Non-Hispanic, male, married, had a program-certified health condition, had a high school diploma or more education and spoke English as their primary language (Table 1). Most first visits occurred in 2010 or later. Compared to members with private insurance, significant increased differences from members with public health insurance were: Hispanic (34.9%, 95% CI 22.0%, 47.8%); slightly older on September 11, 2001 (2.7 years, 95% CI 1.2, 4.2); not high school graduates (25.2%, 95% CI 10.0%, 40.4%); spoke Spanish as their primary language (36.9%, 95% CI 22.9%, 50.9%); and had 2001 annual incomes under $30,000 (21.8%, 95% CI 6.2%, 37.4%).

3.2. Outcomes

Most of the marginalized GRCCC months between monitoring visits were similar to the advantaged (reference) groups' months between monitoring visits, however even the statistically significant differences were not substantial (three or more months) (Table 2). For example, for every five years increase in age, members in the primary analysis attended monitoring visits two and a half (95% CI −2.5, −2.4) months sooner than those 5 years younger. Black GRCCC members attended monitoring visits −0.8 (95% CI -1.3, −0.2) months apart and Hispanic members −0.7 (95% CI -1.4, 0.1) months apart, i.e., sooner than White and non-Hispanic members. The comorbidity sensitivity analysis reference values were generally one-to-two months shorter than in the primary analysis, but members with marginalized and advantaged SDOH still had similar monitoring use frequency in the sensitivity analysis. For example, on average, Black −0.5 (95% CI -1.0, 0.0) and Hispanic −0.4 (95% CI -1.1, 0.3) members attended visits about half a month sooner than White members in the comorbidity sensitivity analysis. The analyses including members with missing SDOH or covariate data produced similar results although the larger sample sizes had narrower confidence limits (Supplemental Table 1).

The monitoring visits attendance ≤18 months apart results (Table 3) are consistent with the months between visits, indicating no substantial differences between marginalized and advantaged members (Table 3). For every five years increase in age, GRCCC members made monitoring visits ≤18 months apart 1.43 times more than those 5 years younger (95% CI 1.41, 1.45). On average, Black and Asian members made slightly more monitoring visits ≤18 months apart than White members. The direction and magnitude of the associations and the 95% confidence intervals were very similar across the primary and the sensitivity analyses. The sensitivity analysis results that included GRCCC members not seen after December 31, 2021 were extremely similar to those excluding them. The minimally adjusted sensitivity analysis also produced similar results: 5-year age difference (OR = 1.44, 95% CI 1.43, 1.46), race (Black vs. White OR = 0.90, 95% CI 0.85, 0.95), sex (OR = 0.91, 95% CI 0.87, 0.96). The analyses including members with missing data also produced similar results (Supplemental Table 2).

Overall, the %MaxVisits generally ranged between 69% and 78% in the primary and comorbidity sensitivity analyses (Table 4). On average, Black members made 75.3% of the maximum visits in the primary analysis and 77.6% in the comorbidity sensitivity analysis, very similar to the White members (primary 72.9% and sensitivity 75.0%, respectively). However, when the COVID-19 period (from March 1, 2020, onwards) was excluded the %MaxVisits was generally a bit lower than in the primary analysis or comorbidity sensitivity analysis. The %MaxVisits was nearly identical in analyses that excluded the COVID-19 period whether the analyses included or excluded missing SDOH or covariate data (Supplemental Table 3).

4. Discussion

This study demonstrates that the WTC Health Program achieved remarkably similar GRCCC monitoring visit participation across SDOH groups. There were no notable differences between the marginalized and advantaged groups.

Although most GRCCC members had private health insurance coverage, those with SDOH characteristics commonly associated with social marginalization were more likely to be covered by public insurance. Nevertheless, in contrast to national U.S. data, attendance at cohort monitoring visits did not vary by insurance type (Keisler-Starkey K; Bunch LN, 2021; Shrider EA, 2021) The program has dedicated staff who reach out to members every year to encourage returning for their next monitoring visit. The staff make special efforts to bridge ethnic, language, educational and other barriers to provide health care monitoring and treatment to eligible members. Such outreach may also be common outside of the program where scheduled visit confirmation and language services exist. However, the %MaxVisits was slightly higher in the primary analysis and comorbidity sensitivity analysis that included the COVID-19 pandemic period, than in the sensitivity analysis that excluded the pandemic period. This may suggest that the WTC program's special efforts, including the rapid implementation of telehealth services to maintain clinical monitoring during the pandemic (Senay et al., 2021) helped sustain or even increase monitoring visit utilization. This contrasts with the broader U.S. experience, where primary health care availability and use declined during the peak pandemic period (Tu et al., 2022). No-cost health monitoring and partial treatment cost coverage does not fully account for the similar use across SDOH characteristics, as the 58% of GRCCC employed in protective services, who already have private health insurance and thus access to care, made monitoring visits slightly more often than other members.

Clinic and other characteristics may also contribute to the strong similarity of program participation. Most active GRCCC members still live in the New York metropolitan area served by the program's five Clinical Centers of Excellence, which may minimize many barriers to access care including transportation. However, the program does not support transportation costs to reach the clinics, and clinic-specific capacity constraints can also influence access to their care. Prior investigations have examined WTC-related program utilization. A study of WTC rescue and recovery workers and volunteers found socio-demographic characteristics associated with program participation, however their study populations were distinct.(Ayers et al., 2025) Another investigation observed less program participation among younger members, as did our study.(Liu et al., 2025).

This study employed robust analyses appropriate for repeated measures methods of a relatively socio-demographically diverse, large cohort covering seventeen years of observation. While the outcome %MaxVisits may be right skewed as visits less than 11 — 12 months apart are atypical, leaving little opportunity for members to approach a perfect 100%, the 95th percentile of %MaxVisits somewhat balances out any skewedness. Each comparison simultaneously adjusted for all other assessed variables. The similar frequency between the primary and sensitivity results, between analyses excluding and including members with missing SDOH data, and between the full model adjusted results and those with minimal adjustments indicate that variable collinearity did not influence the results, and unmeasured confounding could only minimally account for our results. Many members did not report their race or ethnicity, which could bias the study results. Our analyses excluded GRCCC with any missing data, however the results were nearly the same in analyses that incorporated a separate stratum for missing data in each SDOH category, except the larger sample analyses produced narrower confidence limits.

The majority of GRCCC members are White men whose primary language is English, and therefore the cohort over-represents individuals with less diversity and who may be more likely to normally use health care than the general U.S. population.(Keisler-Starkey K; Bunch LN, 2021) The GRCCC distribution of average age across their visits (48.0 ± 10.2 years) is similar to that of the general U.S. adult population, but importantly underrepresents the elderly, who have more chronic conditions, access to Medicare, and tend to use health services more than younger people.(Keisler-Starkey K; Bunch LN, 2021; McWilliams et al., 2003).

5. Conclusions

While the cohort has proportionately fewer people of color, women and elderly and more private health insurance coverage than the general population, the WTC Health Program has achieved remarkably similar health monitoring participation across the socio-economic spectrum, unlike health care use in the United States.

The following are the supplementary data related to this article.

Supplemental Table 1

Average interval in months between adjacent monitoring visits among the General Responder Clinical Centers Cohort World Trade Center Health Program, January 1, 2008 — December 31, 2024^†.

Supplemental Table 2

Odds ratios of making monitoring visits ≤18 months between General Responder Clinical Centers Cohort World Trade Center Health Program January 1, 2008 — December 31, 2024^†.

Supplemental Table 3

Percent of the maximum number of visits made in General Responder Clinical Centers Cohort World Trade Center Health Program members January 1, 2008 — February 29, 2020^†,††.

Authors Contribution

Moshe Z Shapiro conducted the data analysis. Moshe Z Shapiro, Susan L Teitelbaum, Christopher R Dasaro, Annie Lok and Nancy L Sloan contributed to the study conception and design. Andrew C Todd contributed to data acquisition. Material preparation and analysis were performed by Moshe Z. Shapiro and Christopher R Dasaro. The first draft of the manuscript was composed by MZS, NLS, CRD, and SLT and all authors participated in the interpretation of the data and drafting or revising the manuscript for important intellectual content. All authors read and approved the final manuscript.

CRediT authorship contribution statement

Moshe Z. Shapiro: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Software, Methodology, Investigation, Formal analysis, Conceptualization. Susan L. Teitelbaum: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Software, Methodology, Investigation, Funding acquisition, Conceptualization. Christopher R. Dasaro: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Software, Resources, Project administration, Methodology, Investigation, Formal analysis, Conceptualization. Annie Lok: Writing – review & editing, Methodology. Andrew C. Todd: Writing – review & editing, Visualization, Project administration, Funding acquisition. Nancy L. Sloan: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Software, Project administration, Methodology, Investigation, Formal analysis, Conceptualization.

Ethics approval

This research, last approved on February 3, 2023 by the Icahn School of Medicine at Mount Sinai (previously Mount Sinai School of Medicine) Institutional Review Board (approval number 15–1266), was conducted according to the World Medical Association Declaration of Helsinki (1975, revised 2013) and in accordance with national and institutional committees' standards regarding human studies. Written informed consent was obtained for all participants included in the study.

Disclaimer

The contents of this report are the sole responsibility of the authors and do not necessarily represent the official views of, nor an endorsement, by the National Institute for Occupational Safety and Health (NIOSH), the Centers for Disease Control and Prevention of the U.S. Department of Health and Human Services (CDC/HHS), or the U.S. Government.

Funding source

The study sponsors reviewed the manuscript; they played no role in the study design, collection, analysis or interpretation of the data, the composition or approval of the manuscript, or the decision to submit the manuscript for publication.

Funding

This work was supported by the Centers for Disease Control and Prevention/National Institute for Occupational Safety and Health (cooperative agreements and contracts 200–2002-00384, U10-OH008216/23/25/32/39/75, 200–2011-39,356/61/77/84/85/88, 200–2017-93,325/28/29/30/31/32 and 75D30122C15187).

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data availability

The relevant data are available within the manuscript. De-identified datasets, data dictionary may be requested of the corresponding author for re-analysis of the current study. The data can be made available via a secure website upon submission of the World Trade Center Data Center Data Use Agreement and Data Request Form (including an attestation) and requisite IRB approval.